Hallo Joy,

we use benzoic acid with a d18O around +24 ‰, 3,4,5-trimethoxybenzoic 
acid with a d18O of around +13 ‰ and 2,3-dimethoxybenzoic acid with a 
d18O around -0.3 ‰ (all d18O vs. V-SMOW). Di- and trimethoxy benzoic 
acid are from Acros Organics (http://www.acros.com/).
I would expect that O in carboxyl groups is relatively more enriched in 
18O in comparison to -OH or -OCH3 groups.
Greetings

Roland


Joy Davis wrote:

> Hello all. I’m looking for an organic sample that can be used as an 
> internal reference for oxygen analyses with a d18O near 10 permil. 
> Please let me know if you have or know of such a beast.
>
> Thanks.
>
> - joy
>
> --------------------------------------------------------------
>
> Joy Davis
>
> Ph.D. Candidate
>
> Ocean, Earth & Atmospheric Sciences
>
> Old Dominion University
>
> Norfolk VA
>
> --------------------------------------------------------------
>